This article presents an experimental and numerical analysis of cooling buildings using night-time cold accumulation in phase change material (PCM), otherwise known as the ‘free-cooling principle’. Experimental and numerical studies of the ceiling and floor free-cooling principle, as well as passive cooling, are presented. The free-cooling principle is explained and some of the types of PCMs suitable for summer cooling are listed. An experiment was conducted using paraffin with a melting point of 22°C as the PCM to store cold during the night-time and to cool hot air during the daytime in summer. Air temperatures and heat fluxes as a function of time and dimensionless cold discharging values are presented for different air velocities. Experimental analysis of one week of measuring under real conditions is presented in order to show how cold storage functions. Copyright © 2007 John Wiley & Sons, Ltd.

When considering the deployment of renewable energy sources in systems, the challenge of their utilization comes from their time instability when a mismatch between production and demand occurs. With the integration of thermal storages into systems that utilize renewable energy sources, such mismatch can be evened out. The use of phase-change materials (PCMs) as thermal storage has a theoretical advantage over the sensible one because of their high latent heat that is released or accumulated during the phase-change process. Therefore, the present paper is a review of latent thermal storages in hydronic systems for heating, cooling and domestic hot water in buildings. The work aims to offer an overview on applications of latent thermal storages coupled with heat pumps and solar collectors. The review shows that phase-change materials improve the release of heat from thermal storage and can supply heat or cold at a desired temperature level for longer time periods. The PCM review ends with the results from one of the Horizon2020 research projects, where indirect electrical storage in the form of thermal storage is considered. The review is a technological outline of the current state-of-the-art technology that could serve as a knowledge base for the practical implementation of latent thermal storages. The paper ends with an overview of energy storage maturity and the objectives from different roadmaps of European bodies.

Building sector still consumes 40% of total energy consumption. Therefore, an improved heating system with Solar Assisted Heat Pump (SAHP) was introduced in order to minimse the energy consumption of the fossil fuels and to lower the carbon dioxide emissions occurring from combustion. An energy analysis of the complex heating system for heating of buildings, consisting of solar collectors (SC), latent heat storage tank (LHS) and heat pump (HP) was performed. The analysis was made for the heating season within the time from October to March for different climatic conditions. These climatic conditions were defined using test reference years (TRY) for cities: Adana, Ljubljana, Rome and Stockholm. The energy analysis was performed using a mathematical model which allowed hourly dynamics calculation of losses and gains for a given system. In Adana, Rome and Ljubljana, it was found that the system could cover 80% of energy from the sun and the heat pump coefficient of performance (COP) reached 5.7. In Stockholm, the maximum COP of 5.12 was reached in March and October.